Method of hot-forming continuously cast aluminum



D. B. COFER June 30, 1970 METHOD OF HOT-FORMING CONTINUOUSLY CASTALUMINUM Filed Sept. 15, 1967 United States Patent 3,517,537 METHOD OFHOT-FORMING CONTINUOUSLY CAST ALUMINUM Daniel B. Cofer, Carrollton, Ga.,assignor to Southrvtre Company, Carrollton, Ga., a corporation ofGeorgia Filed Sept. 15, 1967, Ser. No. 668,003

Int. Cl. B21b 1/18 US. Cl. 72234 Claims ABSTRACT OF THE DISCLOSURE Whatis disclosed herein is a method of hot-forming continuously castaluminum or a similar cast metal comprising feeding the cast metal froma continuous casting machine through a series of roll stands with thecast metal always subjected to a lengthwise compressive force betweenadjacent roll stands in spite of variations in the volume per unit oftime of the cast metal resulting from the operating characteristics ofthe continuous casting machine. In each roll stand the cast metal iscompressed to a smaller cross-sectional area and the lengthwisecompressive force to which the cast metal is subjected between all rollstands is achieved by always feeding the cast metal toward a roll standat a greater volume per unit of time than is required to adequately fillthe space defined by the rolls of the roll stand but at not so great avolume per unit of time as to cause fins or cobbles.

BACKGROUND OF THE INVENTION Field of the invention This inventionrelates to hot-forming a cast metal and more particularly, to a methodof hot-rolling a cast metal passed to a rolling mill from a continuouscasting machine by using a plurality of roll stands and in which thecast metal is always subjected to a limited lengthwise compressive forcebetween adjacent roll stands.

Prior art In the manufacture of metal rod from molten metal, a castmetal from a continuous casting machine is characteristically processedthrough a series of roll stands which progressively reduce thecross-sectional area of the cast metal until the desired rodconfiguration is obtained. Each roll stand is constructed so that theconcave peripheries of two or more rolls are disposed about the path ofthe cast metal as the cast metal is passed through the roll stand, andthe area defined by the peripheries of the rolls is smaller than thecross-sectional area of the cast metal as it enters the roll stand. Therolls of each roll stand are driven by a driving means at apredetermined speed, but because of the reduction in cross-s'ec tionalarea of the cast metal in the roll stand, the linear velocity of thecast metal is higher when the cast metal leaves the roll stand than whenthe cast metal enters the roll stand. Thus, the rolls of each successiveroll stand are driven at a higher speed than the rolls of the precedingroll stand.

As the cast metal from a continuous casting machine is processed throughthe roll stands of a rolling mill as generally described above,lengthwise tensive or compressive forces may be applied to thoseportions of the cast metal extending between adjacent roll stands. Whenone roll stand feeds the cast metal toward a subsequent roll stand at avolume per unit of time which tends to be greater than the subsequentroll stand is able to accept, a lengthwise compressive force is appliedto the cast metal. When this lengthwise compressive force exceedsacceptable limits, it causes the subsequent roll stand to be excessivelyoverfilled with cast metal so that the cast metal in passing through thesubsequent roll stand is urged into gaps between adjacent rolls of theroll stand to form undesirable ribs or fins on the cast metal. When thislengthwise compressive force is excessive, the subsequent roll standdoes not accept all of the cast metal being urged into it and a cobbleis formed in the cast metal. This requires that the mill be shut downuntil the cobble is removed.

A lengthwise tensive force is applied to the cast metal extendingbetween adjacent roll stands when one roll stand feeds the cast metal ata volume per unit of time insufficient to adequately fill the spacedefined by the rolls in a subsequent roll stand so that the subsequentroll stand tends to pull the cast metal toward it. A lengthwise tensiveforce applied to the cast metal extending between adjacent roll standsmay result in stretching the cast metal so that it breaks or inimproperly reducing the crosssectional area of the cast metal.

These problems resulting from lengthwise tensive and compressive forcesare particularly significant where the cast metal is a non-ferrous metalsuch as aluminum that is passed directly from a continuous castingmachine to a rolling mill since the cast metal is relatively easy tocobble with a lengthwise compressive force or break with a lengthwisetensive force and since a continuous casting machine characteristicallyfeeds cast metal to a rolling mill at various volumes per unit of timewhich tend to cause overfilling or underfilling of the roll stands andresulting compressive and tensive forces. Moreover, regardless of theparticular cast metal, another result of inadequately filling the spacedefined by the rolls of a roll stand in addition to a tensive force isthat the cast metal is processed with a flat side; that is, the castmetal will not be formed with a shape corresponding to that defined bythe rolls of the roll stand.

SUMMARY OF THE INVENTION The invention disclosed herein comprises amethod of hot-forming a cast metal fed from a continuous casting machinethrough a series of roll stands in which the cast metal between adjacentroll stands is always subjected to a limited lengthwise compressiveforce, the compressive force being applied to the cast metal regardlessof variations in the volume per unit of time of the cast metal.Specifically, the invention includes feeding a cast metal in apredetermined range of volumes per unit of time from one roll stand to asubsequent roll stand so that the space defined by the rolls of thesubsequent roll stand is always sufficiently filled to subject the castmetal to a lengthwise compressive force but never becomes so excessivelyfilled as to cause ribs or fins on the cast metal or the cobbling of thecast metal.

Accordingly, it is an object of this invention to provide a method ofhot-forming cast aluminum, or a similar metal Without creating flats,fins or cobbles.

Another object of this invention is to provide a method of hot-forming acast metal through a plurality of roll stands wherein the cast metal isnot subjected to a tensive force.

Another object of this invention is to provide a method of hot-forming acast metal wherein the spaces defined by the rolls of the roll stands ofa rolling mill are set prior to operating the rolling mill so that whenthe rolling mill is subsequently operated, only lengthwise compressiveforces within an acceptable range are applied to the cast metal betweenthe roll stands.

Another object of this invention is to provide a method of hot-forming acast metal through a plurality of roll stands, wherein the cast metal isworked to an optimum extent by the rolls of each roll stand.

Another object of this invention is to provide a method of hot-forming acast metal to achieve the foregoing and other objects where the castmetal is cast in a continuous casting machine and is fed directly to arolling mill at a hot-forming temperature and at various volumes perunit of time within the range of volumes.

Other objects, features and advantages of the present invention willbecome apparent upon readingthe following specification, 'when taken inconjunction with the accompanying drawing.

BRIEF DESCRIPTION OF THE DRAWING FIG. 1 is a schematic illustration of acontinuous casting apparatus with which the method disclosed herein maybe used, showing a cast bar as it is passed from a continuous castingmachine through a series of roll stands in a rolling mill;

FIG. 2 is a cross-sectional view of a cast bar as it is being hot-formedby the rolls of a roll stand having three rolls;

FIG. 3 is a cross-sectional view of a cast bar after it has passed fromthe roll stand of FIG. 2 and is being hot-formed by a subsequent rollstand;

FIG. 4 is a cross-sectional view of a cast bar as it is being hot-formedby the rolls of a roll stand having two rolls;

FIG. 5 is a cross-sectional view of a cast bar after it has passed fromthe roll stand of FIG. -4 and is being hot-formed by a subsequent rollstand;

FIG. 6 is a cross-sectional view of a cast bar as it is being hot-formedin a roll stand, the cast bar being of smaller volume than that requiredto adequately fill the space defined by the rolls of the roll stand;

FIG. 7 is a cross-sectional view of a cast bar as it is being hot-formedin a roll stand, the cast bar being of a volume so large as toexcessively overfill the space defined by the rolls of the roll stand;

FIG. 8 is a partial side elevational view of the rolls of a roll stand,showing the mannerin which the working diameter of a roll is determined.

DESCRIPTION OF THE EMBODIMENTS Referring now more particularly to thedrawing, in which like numerals indicate like parts throughout theseveral views, FIG. 1 shows a continuous casting machine 10 and arolling mill 11. The continuous casting machine 10 serves as a castingmeans for solidifying a molten metal 12, such as molten aluminum pouredfrom a pouring spout 13 into the mold formed between a. casting wheel 14and an endless band 15 extendingalong the periphery of the casting wheel14. As the casting wheel 14 and endless band 15 move in the directionindicated by arrow 16 to carry the molten metal through the lowersegment of casting wheel 14, the molten metal 12 is cooled andsolidified into a cast bar 1 8. The endless band 15 is positionedagainst the lower segment of casting wheel 14 by a plurality of idlerwheels 17. After solidification in the annular groove in the peripheryof casting wheel 14, the cast bar 18 is directed away from the peripheryof casting wheel 14 and passed directly to the rolling mill 11 at ahot-forming temperature.

The rolling mill 11 comprises a plurality of roll stands 20 disposed inalignment with one another. Roll stands 20 each include a plurality ofrolls which engage the cast bar 18. As is shown in FIGS. 2-5, the rollsof each roll stand 20 may be two or more in number and arrangeddiametrically opposite from one another (FIGS. 4 and 5) or arranged atequally spaced positions about the axis of movement of the cast bar 18through the rolling mill 11. The rolls of each roll stand 20 of therolling mill 11 are rotated at a predetermined speed by a power meanssuch as one or more electric motors (not shown) and the casting wheel 14is rotated at a speed generally determined by its operatingcharacteristics. The rolling mill 11 serves to hot-form the cast bar 18into a rod 21 of a cross-sectional area substantially less than that ofthe cast bar 18 as it enters the rolling mill 11.

As is shown in FIGS. 2 and 3, and in FIGS. 4 and 5, the peripheralsurfaces of the rolls of adjacent roll stands in the rolling mill 11change in configuration; that is, the cast bar 18 is engaged by therolls of successive roll stands 20 with surfaces of varyingconfiguration, and from difierent directions. This varying surfaceengagement of the cast bar 18 in the roll stands 20 functions to kneador shape the metal in the cast bar 18 in such a manner that it is workedat each roll stand and also to simultaneously reduce and change thecross-sectional area of the cast bar 18 into that of the rod 21.

As each roll stand 20 engages the cast bar 18, it is desirable that thecast bar 18 be received with sufficient volume per unit of time at theroll stand 20 for the cast bar 18 to generally fill the space defined bythe rolls of the roll stand so that the rolls will be effective to workthe metal in the cast bar 18. However, it is also desirable that thespace defined by the rolls of each roll stand 20 not be overfilled sothat the cast bar 18 will not be forced into the gaps between the rolls.Thus, it is desirable that the rod be fed toward each roll stand 20 at avolume per unit of time which is sufficient to fill, but not overfill,the space defined by the rolls of the roll stand 20.

As the cast bar 18 is received from the continuous casting machine 10,it usually has one large flat surface corresponding to the surface ofendless band 15 and inwardly tapered side surfaces corresponding withthe shape of the groove (not shown) in casting wheel 14. As cast bar 18is compressed by the rolls 22 such as those shown in FIG. 2, the castbar 18 is deformed so that it generally takes the cross-sectional shapedefined by the adjacent peripheries of the rolls as shown in FIG. 2. Thecast bar 18 will be kneaded or worked and its surfaces will conform tothe surfaces 30 of V-shaped grooves 25. If the volume of the cast bar 18fed to the roll stand is adequate generally to fill the space defined bythe rolls 22, voids 27 will be defined between the cast bar 18 and thecentral recesses 26 of each roll 22, and voids 23 will be definedbetween the cast bar 18 and the portions of the V surfaces 30 adjacentthe flat peripheral surfaces 28 of the rolls. Generally, the voids 27defined at the central recesses 26 of the rolls 22 will be approximatelyequal in volume to the voids 23 defined adjacent the fiat peripheralsurfaces 28 between the surfaces 30 of the rolls and the cast bar 18.Thus, each surface 30 of each roll generally has an area of contact 31with the cast bar 18 extending only over a central portion of eachsurface 30 when the space defined by the rolls has been adequatelyfilled with the cast bar 18.

As is shown in FIG. 3, the roll stand subsequent to the roll stand ofFIG. 2 generally has rolls 32 disposed at 120 degree intervals about theaxis of movement 29 of the cast bar 18, but oriented 60 degrees aroundthe axis 29 from the rolls 22 of FIG. 2. Also, rolls 32 are formed withconcave surfaces 35 which change the cross-sectional shape of the castbar 18 into the shape of a triangle with convex sides. While rolls 32 ofFIG. 3 do not define a central recess such as central recess 26 of therolls 22 of FIG. 2, small voids 37 are defined between adjacent rolls32, similar to the voids 23 defined by rolls 22 of FIG. 2.

If the rolling mill 11 utilizes only two rolls at each roll stand 20, asshown in FIGS. 4 and 5, the peripheral surfaces of the rolls areconstructed usually with alternately V-shaped and concave grooves. As isshown in FIG. 4, rolls 38 define V-shaped grooves 40, the legs of the Vbeing angled at approximately degrees. Each roll 38 defines a centralrecess 41 at the center of its V and flat peripheral surfaces 42 on eachside of its groove 40. When a cast bar 18 of a volume adequate to fillthe space defined by the rolls 38 is received by the roll stand, smallvoids 43 and 43a are defined between the cast bar 18 and those portionsof the working surfaces 44 of the rolls 38 which are adjacent thecentral recesses 41 and the flat peripheral surfaces 42. Thus, theworking surfaces 44 of each V-shaped groove provide areas of contactwith the cast bar 18 which are bounded by voids 43 and 43a. As is shownin FIG. 5, the roll stand which is usually subsequent to the roll standshown in FIG. 4 works the cast bar 18 from sides opposite to the sidesof the cast bar 18 engaged by the roll stand of FIG. 4 with rolls 39disposed 90 degrees about the cast bar 18 from the rolls 38 of theprevious roll stand. The concave surfaces 46 of the rolls 39 generallyengage the cast bar 18 throughout their center areas, while voids 47 aredefined toward the sides of rolls 39.

As is shown in FIG. 6, when the space defined by the rolls of a rollstand is not adequately filled with a cast bar 18 the cast bar 18 isreshaped by compression only to conform with the limited portions of therolls which engage the cast bar 18; that is, a portion of the cast bar18 received by a roll stand 20 will not be compressed and a flat orother flaw will be created in the cast bar 18. Moreover, a roll stand 20which is not adequately filled with a cast bar 18 is not effective toproperly work the cast bar 18. Furthermore, the rolls of a roll stand 20are driven at a speed to hot-form a particular volume per unit of timeand an inadequately filled roll stand such as that shown in FIG. 6 willtend to pull additional cast bar 18 into the roll stand, thus applying atensive force to the cast bar 18 bet-ween the inadequately filled rollstand and the preceding roll stand.

As is shown in FIG. 7, when the space defined by the rolls of a rollstand 20 is excessively overfilled with a cast bar 18, the cast bar 18will entirely fill the space in the roll stand, including voids 23, 27,37, 43 or 43a described above and fins or ribs 51 will be formed on thecast bar 18 in the voids. Of course, further overfilling the spacedefined by the rolls may result in an excessive compressive force beingapplied to the cast bar 18 and in a cobble requiring the shut-down ofthe rolling mill 11.

In order to avoid the situations shown in FIGS. 6 and 7 with roll stands20 such as those shown in FIGS. 2-5, it is necessary to provide anacceptable range of volumes per unit of time of the cast bar 18 to eachroll stand 20 of a rolling mill 11. This acceptable range should serveto apply a lengthwise compressive force to the cast bar 18 as it passesbetween adjacent roll stands; however, the amount of compressive forceshould be limited so as never to be so great as to cause the cast bar 18to excessively overfill the space defined by the rolls of a roll stand20 and create fins or cobbles.

In providing an acceptable range of volumes per unit of time of the castbar 18, it is desirable to control the volume per unit of time of thecast bar 18 passing between adjacent roll stands 20 in terms of theratio of the bar volume of the cast bar 18 leaving a roll stand per unitof time to a stand volume that expresses the volume of the cast bar 18which Will pass through the roll stand per the same unit of time withouta tensive or compressive force being applied to cast bar 18 between theroll stand and the preceding roll stand. This ratio multiplied by 100from convenience of expression relative to 100 provides a mill constantby which bar volume and stand volume are related and with which anacceptable range of volumes per unit of time of the cast bar 18 to befed to each roll stand 20 of a rolling mill 11 is conveniently defined.

The stand volume indicative of the cast bar 18 which can be hot-formedby a roll stand while applying no tensive or compression forces to thecast bar 18 as it is fed from the preceding roll stand can be computedby the following formula:

where SV equals stand volume, r.p.m. equals revolutions per minute ofthe rolls of the roll stand, WC equals working circumference of therolls of the roll stand, and SA is the stand area or the minimumcross-sectional area of the cast bar 18 required to adequately fill thespace defined by the rolls of the roll stand as measured by the area ofa circle 55 perpendicular to the axis 29 and inscribed within andengaging the rolls of the roll stand. The stand volume is convenientlycomputed in cubic feet per minute. The working circumference is thecircumference of a roll where the circle 55 touches the roll and isestimated for rolls in each roll stand 20 by the following formula, andas illustrated in FIG. 8:

where WC equals working circumference of a roll, D equals the outsidediameter of the roll, b equals the distance from the center of thecentral recess 26 of the roll to the center of the circle 55 inscribedwithin the rolls of the roll stand, c equals the radius of the circle 55extending to the point of contact of the circle 55 with the roll, and Aequals the angle in degrees inscribed between b and c. When rolls of thetype shown in FIG. 2 are utilized in a roll stand 21?, each of the rollshas a V-shaped groove with 120 degrees inscribed between the sides ofthe groove and A equals 30 degrees.

The bar volume of the cast bar 18 leaving a roll stand 20 per unit oftime is computed by the following bar volume formula:

where BV equals bar volume, LF equals linear feet of the cast bar 18 perminute leaving the roll stand, and BA equals the cross-sectional area ofthe cast bar 18 as it leaves the roll stand.

It will be understood that the mill constant of a roll stand resultingfrom the ratio of the bar volume as defined by Equation 3 to the standvolume as defined by Equation 1 indicates whether the space defined bythe rolls of the roll stand is underfilled, overfilled, or excessivelyoverfilled with the cast bar 18 relative to that filling of the rollstand corresponding to SA at which no tensive or compressive forces areapplied to the cast bar 18 as it passes to the roll stand from thepreceding roll stand. This is because a mill constant greater thanindicates overfilling and a mill constant less than 100 indicatesunderfilling relative to that filling of the space defined by the rollsof the roll stand corresponding to SA at which no tensive or compressiveforces are applied to the cast bar 18 between the roll stand and thepreceding roll stand.

As previously explained, it is desirable to have a compressive forceapplied to the cast bar 18 as it passes between adjacent roll stands 20.If the cast bar 18 is fed to a roll stand at a volume per unit of timein excess of the stand volume, the mill constant will be in excess of100 and, a compressive force will be applied to the cast bar 18extending between that roll stand and the one preceding it. Thus, thesituation of underfilling illustrated in FIG. 6, which creates a fiat orflattened area on the cast bar 18, or which applies a tensive force tothe cast bar 18, is avoided.

In providing a mill constant in excess of 100 at each roll stand in arolling mill, the volume of the cast bar 18 to be fed from thecontinuous casting machine 10 to the rolling mill '11 must be initiallyconsidered. This is because both the speed of the continuous castingmachine 10 and the cross-sectional area of the cast bar 18 as it passesfrom the continuous casting machine 10 vary within ranges characteristicof the particular casting machine 10 so that the volume of the cast bar18 per unit of time entering the first roll stand of a rolling mill 11varies within a predetermined range of volumes. Thus, the stand area(SA) of the first roll stand must be selected so that the stand volumeSV of the first roll stand is less than the volume of the cast bar 18per unit of time entering the roll stand throughout the range of volumesof the cast bar 18 provided by the operating characteristics of thecasting machine 10. This results in the first roll stand always having amill constant greater than 100 regardless of variations in the cast bar18 entering the roll stand.

Once the stand area (SA) is established for the first roll stand, therange of bar volumes (BV) leaving the first roll stand is known and thestand area (SA) for the next roll stand is selected to provide a millconstant which is always greater than 100 as the volumes per unit oftime of the cast bar 1 8 from the first roll stand vary. The stand areas(SA) for subsequent roll stands are similarly selected to insure a millconstant for each roll stand which is always in excess of 100 regardlessof variations in the volume of the cast bar 18 fed to each roll stand.

Thus, at the particular predetermined r.p.m. of each roll stand, eachroll stand receives a volume of the cast bar 18 which is in excess ofthat required to adequately fill the roll stand as defined by SV. Interms of roll stand constants, each roll stand has a mill constant whichis always in excess of 100 regardless of the variations in the volume ofthe cast bar 18 which result from operating characteristics of thecontinuous casting machine 10. Since the r.p.m. of each preceding rollstand is less than the r.p.m. of a subsequent roll stand, the stand area(SA) stants in each roll stand below about 115. However, it has beenfound, through experimentation, that with most continuous castingmachines 10 used for casting aluminum, a nominal mill constant of 106 isadequate to prevent variations in the volume of a cast bar 18 fromcausing an actual mill constant greater than 115 and less than 100 withthe result that a compressive force is always applied to the cast bar 18between roll stands but the compressive forces are never so large as tocause fins, ribs, or cobbles.

A rolling mill 11 having a nominal mill constant of 106 at each rollstand has been successively operated with a continuous casting machine10 operating at substantially constant speed but with thecross-sectional area of the cast bar 18 as it passes from the continuouscasting machine varying between 3.08 and 3.24 square inches. The rollingmill 11 was shut-down several times and fish poles were extracted andmeasured to determine that the rolling mill 11 was operating inaccordance with the invention. The following table shows the results ofthe various measurements made at each of fifteen roll stands for each offive cast bars 18:

Roll #1, 21.438 r.p.m., WD =8.923

in. Vel= 50.08 f.p.n1. l\

R011 #2, 26.787 r.p.m.; WD =9.1795

in.; Vel=64.38 f.p.m. M

Roll #3, 33.47 r.p.m.; WD=9.202

in.; Vel=81.42 f.p.rn

Roll #4, 41.817 r.p.m.;

in.; Vel=103.83 f.p.m.

Roll #5, 52.34 r.p.m.; WD=9.5756

in.; Vel=l31.25 f.p.n1.

Roll #6, 65.41 r.p.m.; WD=9.7525

in.; Vel=166.5 f.p.m.

Roll #7, 81.73 r.p.m.; WD 9.9126

in.; Vel=209.58 f.p.rn.

Roll #8, 102.125 r.p.m.; WD 9.9126 in.; Vel=265.0 f.p.m.

Roll #9, 128.19 r.p.m.; WD =9.9683

in.; Vel=334.5 r.p.m.

Roll #10, 160.17 r.p.m.; WD

10.0598 1n.;Vel=421.8 f.p.m. MC

- Roll #11, 200.13 r.p.m.; WD=

10.176 in.; Vel= 666.2 f.p.m.

Roll #12, 250.07 r.p.m.; WD=

12.1997 in.; Vel=832.8 1.13.111.

Roll #13, 311.9 r.p.m.; WD

10.1997 in.; Vel=832.8 f.p.m.

Roll #14, 389.7? r.p.m.; WD 10.268

in.; Ve1= 1047.7 r.p.m.

Roll #15, 486.96 r.p.m.; WD

10.2861 in.; Vel=1311.3 f.p.m.

Cast bar Bar area in. 526 525 521 520 524 1C 106. 106. 18 105. 27 105.01 105.89 Bar area in. 403 413 409 407 414 M 102. 80 105. 25 104. 41103. 77 105.

Bar area in. .329 33 .337 33 .33

1670 1667 1672 1662 166 06.06 105. 87 106. 19 105. 55 105. 93 Bar areain. 1330 1365 1321 1354 1358 06. 26 109.06 105. 55 108. 18 108. 50 Bararea in. 1090 .1114 .1119 1115 1112 109.0 111. 4 111. 9 111.5 111. 2

defined by the rolls of successive roll stands progressively decreasesand the required mill constants are readily achieved with stand areas(SA) which provide a specific size of the rod 21 from the last rollstand.

In selecting mill constants for the roll stands of a rolling mill 11,each roll stand may be regarded as having a nominal mill constantcorresponding to a particular volume of the cast bar 18 from which theactual mill constant varies as the volume of the cast bar 18 varies.Although the nominal mill constants of the roll stands are selected inaccordance with the specific characteristics of a particular continuouscasting machine 10', the nominal mill constant for each roll stand willin most rolling mills 11 be substantially higher than to provide formaximum variation in volume of the cast bar 18 fed to the rolling mill11 from a continuous casting machine 10. However, a practical upperlimit of the actual mill constant is established by the danger ofcobbles and of fins or ribs as shown in FIG. 7 so the nominal millconstant must not be so high as to result in variations in the volume ofthe cast bar 18 causing the upper limit of the actual mill constants tobe too high.

When hot-forming continuously cast aluminum, it has been found thatlimiting the actual mill constants to or lower Will not result in acompressive force which causes the forming of cobbles. Moreover, inorder to avoid fins or ribs in the cast bar 18, it has been founddesirable to limit the upper limit of the actual mill con- It isbelieved that the figures presented in the above table illustrate theeffectiveness of a nominal mill constant of 106 since it will beapparent that regardless of variations in the volume of the cast bar 18resulting from the operating characteristics of the continuous castingmachine 10, the actual mill constant at each of the fifteen roll standswas always in excess of 100 but less than 115. Thus, a limitedcompressive force was applied to the cast bar 18 between adjacent rollstands and upon examining a rod 21 after processing through the rollingmill 11, it was found that virtually no flats, ribs, or fins werepresent on the rod 21. Moreover, no cobbles occurred during rolling andgenerally speaking, a superior product was produced.

It will be obvious to those skilled in the art that many variations maybe made in the embodiments chosen for the purpose of illustrating thepresent invention without departing from the scope thereof as defined bythe appended claims.

I claim:

1. In a method of hot-forming a cast metal bar from a continuous castingmachine, the step of passing the cast metal bar through a series of rollstands and applying a lengthwise force to the cast metal bar as itpasses simultaneously from a first roll stand and into a second rollstand.

2. In a method of hot-forming a cast metal bar, the steps of feeding acast metal bar from a continuous casting machine to a series of rollstands, and

compressing the cast metal bar at each successive roll stand to asmaller cross-sectional area while simultaneously feeding the cast metalbar into a successive roll stand with a preceding roll stand at a volumeper unit of time which is other than that required to adequately fill aspace defined by the rolls of said successive roll stand.

3. In a method of hot-forming a solid metal shape from a continuouscasting machine, the step of applying a compressive force to said solidmetal shape by feeding the solid metal shape simultaneously from a firstroll stand and into a succeeding roll stand at a volume per unit of timegreater than the minimum capacity of said succeeding roll stand.

4. In a method of hot-forming a solid metal shape from a continuouscasting machine, the step of feeding the solid metal shape through aseries of roll stands at a volume rate higher than each roll standoperates to normally accept, said solid metal shape being in at leasttwo of said roll stands simultaneously.

5. In a method of hot-forming a cast metal bar from a continuous castingmachine, the step of passing the cast metal 'bar through a series ofroll stands and maintaining the metal volume of the cast metal barleaving each roll stand per unit of time above that predeterminedminimum volume which Will neither overfill nor underfill the next rollstand.

6. The invention of claim wherein the ratio of the metal volume to theminimum volume multiplied by 100 is in a range between 100 and 125.

7. The invention of claim 5 wherein the ratio of the metal volume to theminimum volume multiplied by 100 is approximately 106.

8. In a method of hot-forming a cast metal which is solidified in acasting means and which is subsequently passed to a hot-forming means ata hot-forming temperature and at a volume per unit of time that variesWithin a range of volumes, said hot-forming means including a pluralityof roll stands each having a plurality of driven rolls defining a rollpass through which a particular volume per unit of time of said castmetal will pass without substantial tensive or compressive forces beingapplied to the said cast metal as said cast metal is fed to said rollpass, and said method including the step of feeding said cast metal fromone roll stand to a subsequent roll stand at a volume per unit of timewhich is always greater than said particular volume per unit of time.

9. The method of claim 8 in which said particular volume per unit oftime for each of said plurality of roll stands is defined by theformula:

where SV is said particular volume per unit of time, rpm. is therevolutions per minute of said driven rolls, SA is the area of a circleinscribed within said driven rolls perpendicular to the axis of movementof said cast metal through said roll pass, and WC is the circumferenceof a driven roll where said circle contacts a surface of said drivenroll.

10. In a method of rolling a cast metal in a plurality of roll standseach having a roll pass defined by a plurality of driven rolls andthrough which said cast metal passes along an axis of movement, the stepof adjusting the area of each roll pass transverse to said axis so thatthe volume of cast metal per unit of time passing through said each rollpass as defined by the formula:

is less than the volume of said cast metal leaving said roll pass asdefined by the formula:

where SV is said volume of cast metal per unit of time passing throughsaid roll pass, rpm. is the revolutions per minute of said driven rolls,SA is the area of a circle inscribed within and touching said pluralityof driven rolls perpendicular to said axis, WC is the circumference of adriven roll Where said circle touches to a surface of said driven roll,BV is the volume of said cast metal leaving said roll pass, LP is thevelocity in linear feet per minute of said cast metal leaving said rollpass, and BA is the cross-sectional area of said cast metal leaving saidroll pass.

References Cited UNITED STATES PATENTS 2,710,433 6/1955 Properzi 164-283X 2,789,450 4/ 1957 Properzi 72-224 2,904,829 9/1959 Heck 72-224 X3,017,665 1/1962 Dasher et a1 18-9 MILTON S. MEHR, Primary Examiner US.Cl. X.R. 72-224, 336

UNITED STATES PATENT OFFICE 69 CERTIFICATE OF CORRECTION Patent No.3,517,537 D t d June 30 1970 Inventor) D. B Cofer It is certified thaterror appears in the above-identified patent and that said LettersPatent are hereby corrected as shown below:

The ti tle of the invention is changed from "METHOD OF HOT-FORM I NGCONTNUOUSLY CAST ALUMINUM to read-METHOD 0F HOT-FORMING CONTINUOUSLYCAST METAL".

Signed and sealed this 28th day of December 1 971 (LBEAL) fittest:

EEDWARD M.FLETCHER,JR. Attesting Officer ROBERT GOTTSCHALK ActingCommissioner of Patents

